An image forming apparatus of an ink jet type records on a printing medium by discharging ink from a print head during reciprocating motion in a main scanning direction. It forms an image by repeated recording in the main scanning direction while conveying the printing medium in a sub-scanning direction by means of a conveying roller. Generally, when conveying a printing medium, such as paper, on a conveying roller and the like, there are variations in the amount of conveyance (feed rate) depending on the mounting condition of the conveying roller, type of printing medium, and the like. Thus, patent document 1 discloses a technique for determining a correction value for the amount of conveyance based on printing results of a plurality of test patterns recorded using different correction values. That is, this technique selects the pattern which gives the best printing result from among the recorded test patterns and thereby determines a parameter for use to drive the conveying roller.
(Patent document 1) Japanese Patent Laid-Open No. 2003-011344